Capacitive sensing measures a capacitance resulting from two or more conductive surfaces separated by a dielectric. Capacitive sensing is commonly used to detect a change in capacitance resulting from the proximity of a human hand, a touch of a human finger, or a touch of a conductive stylus. Capacitive sensing is commonly used for human interfacing with electronic systems, for example; mobile phones, tablet computers, electronic games, electronic instruments, appliances, automotive systems, and industrial systems.
There are many alternative methods for capacitive sensing. For example, a capacitance may be measured by using the capacitance in an oscillator and measuring the frequency of oscillation. Alternatively, a capacitance may be measured by measuring the attenuation of an AC signal. Alternatively, a capacitance can be measured by measuring the time required to charge the capacitance through a known resistance. Each alternative measurement method has inherent advantages, limitations and tradeoffs involving accuracy, cost, response-time, and so forth. In general, capacitive measurement circuits are affected by temperature, humidity, and electrical noise. There is an ongoing need for improved capacitive sensing.